Modeling of wave propagation and absorption in electron cyclotron resonance ion source plasmas

Abstract

The performance of electron cyclotron resonance ion sources (ECRIS) is critically dependent on the resonant absorption of microwave power. However, currently there is little understanding of the propagation and absorption of electromagnetic waves in these ion sources. Measurement of the electromagnetic fields in a source is difficult without perturbing the plasma, and theory is hindered by the complex interaction between the waves, the plasma, the walls of the device, and the magnetic field. In this paper we present the results of quantitative 1D and qualitative 3D simulations of wave propagation and absorption in an electron cyclotron resonance ion source. The 1D simulations use the hot plasma dielectric tensor, which has not previously been applied to ECRIS modeling. The 3D simulations are the first attempt to include absorption by the plasma in calculating the structure of the electromagnetic fields in an ECRIS. These simulations demonstrate that the wave propagation and absorption is strongly dependent on the plasma. The results of the simulations are compared to experimental measurements of the mode structure, energy absorption, and frequency scaling.